Global Mixed-mode Technology Inc.
G1427
2W Stereo Audio Amplifier
6dB\10dB\15.6dB\21.6dB Selectable Gain Settings
Features
Internal Gain Control, Which Eliminates External Gain-Setting Resistors Depop Circuitry Integrated Output Power at 1% THD+N, VDD=5V --2.0W/CH (typical) into a 4Ω Load --1.2W/CH (typical) into a 8Ω Load Bridge-Tied Load (BTL), Single-Ended (SE) Stereo Input MUX PC-Beep Input Fully differential Input Shutdown Control Available Surface-Mount Power Package 24-Pin TSSOP-P
General Description
G1427 is a stereo audio power amplifier in 24pin TSSOP thermal pad package. It can drive 2.0W continuous RMS power into 4Ω load per channel in Bridge-Tied Load (BTL) mode at 5V supply voltage. Its THD is smaller than 1% under the above operation condition. To simplify the audio system design in the notebook application, G1427 supports the Bridge-Tied Load (BTL) mode for driving the speakers, Single-End (SE) mode for driving the headphone. For the low current consumption applications, the SHDN mode is supported to disable G1427 when it is idle. The current consumption can be reduced to 160µA (typically). Amplifier gain is internally configured and controlled by two terminals (GAIN0, GAIN1). BTL gain settings of 6dB, 10dB, 15.6dB, 21.6dB are provided, while SE gain is always configured as 4.1dB (inverting) for headphone driving. G1427 also supports two input paths, that means two different amplitude AC signals can be applied and chosen by setting HP/ LINE pin. It enhances the hardware designing flexibility.
Applications
Stereo Power Amplifiers for Notebooks or Desktop Computers Multimedia Monitors Stereo Power Amplifiers for Portable Audio Systems
Ordering Information
ORDER NUMBER
G1427F31U Note: U:Tape & Reel (FD): Thermal Pad
ORDER NUMBER (Pb free)
G1427F31Uf
TEMP. RANGE
-40°C to +85°C
PACKAGE
TSSOP-24 (FD)
Pin Configuration
G1427
GND/HS GAIN0 GAIN1 LOUT+ LLINEIN LPHIN PVDD RIN LOUTLIN BYPASS 1 2 3 4 5 6 7 8 9 10 11 24 23 22 21 20 19 18 17 16 15 14 13 GND/HS RLINEIN SHUTDOWN ROUT+ R OUT+ RHPIN VDD PVDD HP/LINE ROUTSE/BTL PC-BEEP GND/HS
Thermal Pad
GND/HS 12
Top View TSSOP-24
Bottom View
Ver: 1.3 Sep 23, 2005
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Global Mixed-mode Technology Inc.
Absolute Maximum Ratings
Supply Voltage, VCC…………………..…..…….….…...6V Operating Ambient Temperature Range TA…….…………………………….……….-40°C to +85°C Maximum Junction Temperature, TJ…..……….….150°C Storage Temperature Range, TSTG….…-65°C to+150°C Reflow Temperature (soldering, 10sec)……..……260°C
Note:
(1) (2)
G1427
Power Dissipation (1) TA ≤ 25°C ………...….…………………………..2.7W TA ≤ 70°C ………...….…………………………..1.7W Electrostatic Discharge, VESD Human body mode..…………………….…………3000(2)
: Recommended PCB Layout : Human body model : C = 100pF, R = 1500Ω, 3 positive pulses plus 3 negative pulses
Electrical Characteristics
DC Electrical Characteristics, TA=+25°C PARAMETER
Supply voltage VDD High-Level Input voltage, VIH Low-Level Input voltage, VIL DC Differential Output Voltage Supply Current in Mute Mode IDD in Shutdown
SYMBOL
VDD VIH VIL VO(DIFF) IDD ISD
CONDITION
SE/ BTL , HP/ LINE , SHUTDOWN , GAIN0, GAIN1 SE/ BTL , HP/ LINE , SHUTDOWN , GAIN0, GAIN1 VDD = 5V,Gain = 2 VDD = 5V VDD = 5V Stereo BTL Stereo SE
MIN
4.5 2 ---------
TYP
5 ----5 7.5 4 160
MAX
5.5 --0.8 50 13 7 300
UNIT
V V V mV mA µA
(AC Operation Characteristics, VDD = 5.0V, TA=+25°C, RL = 4Ω, unless otherwise noted) PARAMETER SYMBOL CONDITION
THD = 1%, BTL, RL = 4Ω G=-2V/V THD = 1%, BTL, RL = 8Ω G=-2V/V Output power (each channel) see Note P(OUT) THD = 10%, BTL, RL = 4Ω G=-2V/V THD = 10%, BTL, RL = 8Ω G=-2V/V THD = 0.1%, SE, RL = 32Ω PO = 1.6W, BTL, RL = 4Ω G=-2V/V PO = 1W, BTL, RL = 8Ω G=-2V/V PO = 75mW, SE, RL = 32Ω VI = 1V, RL = 10KΩ, SE THD = 5% F=1kHz, BTL mode G=-2V/V CBYP=1µF f = 1kHz
MIN
-----------------------------
TYP
2 1.25 2.5 1.6 85 100 60 80 30 >15 68 80
MAX
---------------------------------
UNIT
W
mW
Total harmonic distortion plus noise
THD+N
m%
Maximum output power bandwidth Power supply ripple rejection Channel-to-channel output separation Line/HP input separation BTL attenuation in SE mode Input impedance Signal-to-noise ratio Output noise voltage
BOM PSRR
kHz dB dB dB dB MΩ dB µV (rms)
ZI Vn PO = 500mW, BTL, G=-2V/V BTL, G=-2V/V, A Weighted filter
80 85 See Table 2 --90 --45
Note :Output power is measured at the output terminals of the IC at 1kHz.
Ver: 1.3 Sep 23, 2005
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Typical Characteristics
Table of Graphs
FIGURE THD +N Total Harmonic Distortion Plus Noise Output Noise Voltage Vn PO PD Supply Ripple Rejection Ratio Crosstalk Output Power Power Dissipation vs Frequency vs Output Power vs Output Voltage vs Frequency vs Frequency vs Frequency vs Load Resistance vs Output Power
G1427
1,2,7,8,13,14,19,21 3,4,5,6,9,10,11,12,15,16,17,18,20 22 27 23,24 25,26 28,29 30,31
Total Harmonic Distortion Plus Noise vs Output Frequency
10 5 10
Total Harmonic Distortion Plus Noise vs Output Frequency
5
2 1 0.5 % 0.2 0.1 0.0 5
VDD=5V RL=3Ω BTL Po=1.75W A v=15.6dB
A v=21.6dB
2 1 0.5 % 0.2 0.1 0.05
VDD=5V RL=3Ω BTL,Av=6dB
Po=0.5W Po=1W
A v=6dB
0.0 2 0.0 1 20 50 100 200 50 0 Hz 1k 2k
A v=10dB
0.02 0.01 20
Po=1.5W
50 100 20 0 5 00 Hz 1k 2k 5k 10k 20 k
5k
10k
2 0k
Figure 1
Figure 2
Total Harmonic Distortion Plus Noise vs Output Power
10 5 10
Total Harmonic Distortion Plus Noise vs Output Power
5
15kHz
2 1 0.5 % 0.2 0.1 0.05
VDD=5V RL=3Ω BTL,Av=6dB
15kHz
2 1 0.5
VDD=5V RL=3Ω BTL,Av=10dB
1kHz
% 0.2 0.1
1kHz
20Hz
0.0 5
20Hz
0.02 0.01 3m
0.0 2 0.0 1 3m
5m
10m
20m
50 m
100m W
200 m
50 0m
1
2
3
5m
10m
20m
50 m
100m W
200m
500m
1
2
3
Figure 3
Figure 4
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Global Mixed-mode Technology Inc.
G1427
Total Harmonic Distortion Plus Noise vs Output Power
Total Harmonic Distortion Plus Noise vs Output Power
10 5 10
15kHz
5
15kHz
2 1 0.5 % 0.2 0.1 0.05
2 1 0.5 % 0.2 0.1
1kHz
1kHz
0.02 0.01 3m
VDD=5V RL=3Ω BTL,Av=15.6dB
5m 10m 20m 50 m 100m W
20Hz
0.05
VDD=5V RL=3Ω BTL,Av=21.6dB
5m 10m 20m 50 m 100m W
20Hz
0.02 0.01 3m
200 m
50 0m
1
2
3
200 m
50 0m
1
2
3
Figure 5
Figure 6
Total Harmonic Distortion Plus Noise vs Frequency
10 5 10
Total Harmonic Distortion Plus Noise vs Frequency
5
2 1 0.5 % 0.2 0.1 0.0 5
VDD=5V RL=4Ω BTL Po=1.75W A v=15.6dB
A v=21.6dB
2 1 0.5 % 0.2
VDD=5V RL=4Ω BTL,Av=6dB Po=0.25W Po=1.5W
A v=6dB
0.1 0.05
0.0 2 0.0 1 20
A v=10dB
50 100 200 50 0 Hz 1k 2k 5k 10k 2 0k
0.02 0.01 20
Po=1W
50 100 20 0 5 00 Hz 1k 2k 5k 10k 20 k
Figure 7
Figure 8
Total Harmonic Distortion Plus Noise vs Output Power
10 5 10
Total Harmonic Distortion Plus Noise vs Output Power
5
15kHz
2 1 0.5 % 0.2 0.1 0.05
VDD=5V RL=4Ω BTL,Av=6dB
15kHz
2 1 0.5 % 0.2 0.1 0.0 5
VDD=5V RL=4Ω BTL,Av=10dB
1kHz
1kHz
20Hz
0.02 0.01 3m 0.0 2 0.0 1 3m
20Hz
5m
10m
20m
50 m
100m W
200 m
50 0m
1
2
3
5m
10m
20m
50 m
100m W
200m
500m
1
2
3
Figure 9
Figure 10
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Global Mixed-mode Technology Inc.
Total Harmonic Distortion Plus Noise vs Output Power
10 5 10 5
G1427
Total Harmonic Distortion Plus Noise vs Output Power
15kHz
15kHz
2 1
2 1 0.5 % 0.2 0.1 0.05
1kHz
1kHz
%
0.5
0.2 0.1
0.02 0.01 3m
VDD=5V RL=4Ω BTL,Av=15.6dB
5m 10m 20m 50 m
20Hz
0.05
0.02 0.01 3m
VDD=5V RL=4Ω BTL,Av=21.6dB
5m 10m 20m 50 m 100m W
20Hz
100m W
200 m
50 0m
1
2
3
200 m
50 0m
1
2
3
Figure 11
Figure 12
Total Harmonic Distortion Plus Noise vs Frequency
10 5 10
Total Harmonic Distortion Plus Noise vs Frequency
5
2 1 0.5 % 0.2 0.1 0.05
VDD=5V RL=8Ω BTL,Av=6dB
2 1 0.5
VDD=5V RL=8Ω BTL Po=1W
A v=15.6dB
Po=0.25W Po=1W
% 0.2 0.1 0.0 5
A v=21.6dB A v=6dB A v=10dB
50 100 200 50 0 Hz 1k 2k 5k 10k 2 0k
0.02 0.01 20
Po=0.5W
50 100 20 0 5 00 Hz 1k 2k 5k 10k 20 k
0.0 2 0.0 1 20
Figure 13
Figure 14
Total Harmonic Distortion Plus Noise vs Output Power
10 5 10
Total Harmonic Distortion Plus Noise vs Output Power
5
2 1 0.5 % 0.2
15kHz
VDD=5V RL=8Ω BTL,Av=6dB
2 1 0.5 % 0.2
15kHz
VDD=5V RL=8Ω BTL,Av=10dB
1kHz
0.1 0.05 0.1 0.0 5
1kHz
0.02 0.01 3m
20Hz
5m 10m 20m 50 m 100m W 200 m 50 0m 1 2 3
0.0 2 0.0 1 3m
20Hz
5m 10m 20m 50 m 100m W 200m 500m 1 2 3
Figure 15
Figure 16
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Global Mixed-mode Technology Inc.
G1427
Total Harmonic Distortion Plus Noise vs Output Power
Total Harmonic Distortion Plus Noise vs Output Power
10 5 10
15kHz
2 1 0.5 % 0.2 0.1 0.05
VDD=5V RL=8Ω BTL,Av=15.6dB
5
15kHz
2 1
1kHz
%
0.5
1kHz
0.2 0.1
20Hz
0.05
0.02 0.01 3m
0.02 0.01 3m
VDD=5V RL=8Ω BTL,Av=21.6dB
5m 10m 20m 50 m
20Hz
5m
10m
20m
50 m
100m W
200 m
50 0m
1
2
3
100m W
200 m
50 0m
1
2
3
Figure 17
Figure 18
Total Harmonic Distortion Plus Noise vs Frequency
10 5 10 5
Total Harmonic Distortion Plus Noise vs Output Power
2 1 0.5 % 0.2 0.1 0.05
VDD=5V RL=32Ω SE,Av=4.1dB
2 1 0.5
VDD=5V RL=32Ω SE,Av=4.1dB
Po=50mW Po=75mW
% 0.2 0.1 0.05
15kHz
20Hz
0.02
Po=25mW
50 10 0 200 50 0 Hz 1k 2k 5k 1 0k 20k
0.02
1kHz
2m 5m 10 m W 2 0m 50m 100m 20 0m
0.01 20
0.01 1m
Figure 19
Figure 20
Total Harmonic Distortion Plus Noise vs Frequency
10 5 10 5
Total Harmonic Distortion Plus Noise vs Output Voltage
2 1 0.5 % 0.2 0.1 0.05
VDD=5V RL=10kΩ SE,Av=4.1dB Cout=1000µF
%
2 1 0.5
VDD=5V RL=10kΩ SE,Av=4.1dB Cout=1000µF
0.2 0.1 0.05
15kHz
20Hz
Vo=1Vrms
0.02
0.02
1kHz
2 00m 300 m 400 m 50 0m 7 00m Vo-Outpu t Vol tage-Vrms 1 2 3
0.01 20
50
10 0
200
50 0 Hz
1k
2k
5k
1 0k
20k
0.01 100m
Figure 21
Figure 22
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Supply Ripple Rejection Ratio vs Frequency
+0 -10 -20 -30 -40 d B -50 -60 -70 -80 -90
G1427
Supply Ripple Rejection Ratio vs Frequency
+0 -10 -20 -30 -40
TT
T
T
T
TT
VDD=5V RL=8Ω Cb=1µF BTL A v=21.6dB
d B
VDD=5V RL=8Ω Cb=1µF SE
-50 -60 -70
A v=6dB
-80 -90 -100 20
-100 20
50
10 0
200
50 0 Hz
1k
2k
5k
1 0k
20k
50
100
200
5 00 Hz
1k
2k
5k
10k
20 k
Figure 23
Figure 24
Channel Separation
-20 -25 -30 -35 -40 -45 -50 -55 d B -60 -65 -70 -75 -80 -85 -90 -95 -100 20 50 100 200 5 00 Hz 1k 2k d B
Channel Separation
-20 -25
T
VDD=5V Po=1W RL=8Ω BTL,Av=6dB
-30 -35 -40 -45 -50 -55 -60 -65
VDD=5V Po=1W RL=8Ω SE,Av=4.1dB
L TO R
-70 -75 -80 -85
L TO R
R TO L
5k 10k 20 k
-90 -95 -100 20 50 10 0 200
R TO L
50 0 Hz 1k 2k 5k 1 0k 20k
Figure 25
Figure 26
Output Noise vs Frequency
5 00u 4 00u 3 00u
Output Power vs Load Resistance
2.5
2 00u
1 00u V 70u 60u 50u 40u 30u 20u
Output Power(W)
VDD=5V RL=4Ω BTL,Av=6dB A -Weighted filter
2
1.5
VDD=5V THD+N=1% BTL Each Channel
1
0.5
10u 20
50
100
200
5 00 Hz
1k
2k
5k
10k
20 k
0 0 10 20 Load Resistance(Ω) 30 40
Figure 27
Figure 28
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G1427
Power Dissipation vs Output Power
Output Power vs Load Resistance
0.7 0.6 Output Power(W) 0.5 0.4 0.3 0.2 0.1 0 4 8 12 16 20 24 Load Resistance(Ω) 28 32 VDD=5V THD+N=1% SE Each Channel 1.8 1.6 1.4 Power Dissipation 1.2 1 0.8 0.6 0.4 0.2 0 0
RL=3Ω
RL=4Ω VDD=5V BTL Each Channel RL=8Ω
0.5
1 1.5 Po-Output Pow er(W)
2
2.5
Figure 29
Figure 30
Power Dissipation vs Output Power
0.35 0.3 Power Dissipation(W) 0.25 0.2 0.15 0.1 0.05 0 0 0.2 0.4 Po-Output Pow er(W) 0.6 0.8 RL=8Ω RL=32Ω VDD=5V SE Each Channel
Recommend PCB Footprint
RL=4Ω
Figure 31
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Pin Description
PIN
1,12,13,24 2 3 4 5
G1427
NAME
GND/HS GAIN0 GAIN1 LOUT+ LLINEIN
I/O
I I O I
FUNCTION
Ground connection for circuitry, directly connected to thermal pad. Bit 0 of gain control Bit 1 of gain control Left channel + output in BTL mode, + output in SE mode. Left channel line input, selected when HP/ LINE pin is held low.
6 7,18 8 9 10 11 14 15 16 17 19 20 21 22 23
LPHIN PVDD RIN LOUTLIN BYPASS PC-BEEP SE/ BTL ROUTHP/ LINE VDD RHPIN ROUT+
SHUTDOWN
I I I O I I I O I
Left channel headphone input, selected when HP/ LINE pin is held high. Power supply for output stages. Common right input for fully differential inputs. AC ground for single-ended inputs. Left channel - output in BTL mode, and high impedance in SE mode. Common left input for fully differential inputs. AC ground for single-ended inputs. Tap to voltage divider for internal mid-supply bias generator. The input for PC-BEEP mode. PC-BEEP is enabled when at least eight continuous > 1-VPP (peak to peak) square waves is input to PC-BEEP pin. Hold low for BTL mode, hold high for SE mode. Right channel - output in BTL mode, high impedance state in SE mode. MUX control input, hold high to select headphone inputs (6,20), hold low to select line inputs (5,23). Analog VDD input supply. This terminal needs to be isolated from PVDD to achieve highest performance. Right channel headphone input, selected when HP/ LINE pin is held high. Right channel + output in BTL mode, positive output in SE mode. Places entire IC in shutdown mode when held low, expect PC-BEEP remains active. Right channel line input, selected when HP/ LINE pin is held low.
I O I I
RLINEIN
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Block Diagram
G1427
RLINEIN RHPIN
Right MUX
RIN PC-Beep
PC-Beep
Depop Circuitry
GAIN0 GAIN1 SE/BTL HP/LINE
Gain/MUX Control
LLINEIN LHPIN
Left MUX
LIN
Ver: 1.3 Sep 23, 2005
10
+
BYPASS
+ + + + _ _
ROUTPVDD
Power Management
_ _
GND
ROUT+
VDD SHUTDOWN
_ _ _ _
LOUT+
LOUT-
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Application Circuit
G1427
Right Linein Negative Differential Input 1µF
23 20
RLINEIN RHPIN
Right MUX
Right Hpin/Linein Positive 1µF Differential Input
8 14
RIN PC-Beep BYPASS
PC-Beep
2.2µF 2 3 15 17 5 6 Left Hpin Negative 1µF Differential Input Left Hpin/Linein Positive Differential Input 1µF GAIN0 GAIN1 SE/BTL HP/LINE LLINEIN LHPIN
Left Linein Negative Differential Input 1µF
Gain/MUX Control
Left MUX
10
LIN
Application Circuit Using Differential Inputs
Note: 1µF ceramic capacitor should be placed as close as possible to the IC to filter the higher-frequency noise.
Ver: 1.3 Sep 23, 2005
11
+ +
11
Depop Circuitry
+ +
+
_
1µF PC-BEEP Input Signal
+
ROUT16 VDD 220µF 1K PVDD
Power Management
_ _ _ _
1µF Right Hpin Negative Differential Input
ROUT+
21
7,18 VDD 19 22 1µF 10µF Note 100K 4 220µF 1K
VDD SHUTDOWN 1,12,13,24 GND
LOUT+
LOUT-
3
0.1µF
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Application Circuit (continued)
G1427
Right Linein Input
1µF
23 20
RLINEIN RHPIN
Right MUX
Right Hpin Input
1µF
8 14
RIN PC-Beep BYPASS
PC-Beep
2.2µF 2 3 15 Left Linein Input 1µF 17 5 6 Left Hpin Input 1µF GAIN0 GAIN1 SE/BTL HP/LINE LLINEIN LHPIN
Gain/MUX Control
Left MUX
10 1µF
LIN
Application Circuit Using Single-Ended Inputs
Note: 1µF ceramic capacitor should be placed as close as possible to the IC to filter the higher-frequency noise.
Ver: 1.3 Sep 23, 2005
12
+ +
11
Depop Circuitry
+ +
+
_
1µF PC-BEEP Input Signal
+
ROUT16 VDD 220µF 1K PVDD
Power Management
_ _ _ _
1µF
ROUT+
21
7,18 VDD 19 22 1µF 10µF Note 100K 4 220µF 1K
VDD SHUTDOWN 1,12,13,24 GND
LOUT+
LOUT-
3
0.1µF
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Application Information
Gain setting via GAIN0 and GAIN1 inputs
The internal gain setting is determined by two input terminals, GAIN0 and GAIN1. The gains listed in Table 1 are realized by changing the taps on the input resistors inside the amplifier. This will cause the internal input impedance, ZI, to be dependent on the gain setting. Although the real input impedance will shift by 30% due to process variation from part-to-part, the actual gain settings are controlled by the ratios of the resistors and the actual gain distribution from part-topart is quite good. Table 1 GAIN0
0 0 1 1 X
G1427
AV (dB)
21.6 15.6 10 6 30 45 70 90
Table 2 Zi (Kohm)
Input Capacitor
In the typical application, an input capacitor Ci is required to allow the amplifier to bias the input signal to the proper dc level for optimum operation. In this case ,Ci and the input impedance of the amplifier, Zi, form a high-pass filter with the -3dB determined by the equation: f-3dB= 1/ (2πRI Ci) The value of Ci is important to consider as it directly affects the bass performance of the application circuit. For example, if the input resistor is 15kΩ, the input capacitor is 1µF, the flat bass response will be down to 10.6Hz. Because the small leakage current of the input capacitors will cause the dc offset voltage at the input to the amplifier that reduces the operation headroom, especially at the high gain applications. The low-leakage tantalum or ceramic capacitors are suggested to be used as the input coupling capacitors. When using the polarized capacitors, it is important to let the positive side connecting to the higher dc level of the application.
GAIN1
0 1 0 1 X
SE/ BTL
0 0 0 0 1
AV (dB)
6 10 15.6 21.6 4.1
Input Resistance
The typical input impedance at each gain setting is given in the Table 2. Each gain setting is achieved by varying the input resistance of the amplifier, which can be over 3 times from its minimum value to the maximum value. As a result, if a single capacitor is used in the input high pass filter, the -3dB or cut-off frequency will be also change over 3 times. To reduce the variation of the cut-off frequency, an additional resistor can be connected from the input pin of the amplifier to the ground, as shown in Figure 1. With the extra resistor, the cut-off frequency can be re-calculated using equation : f-3dB= 1/ 2πC(R||RI). Using small external R can reduce the variation of the cut-off frequency. But the side effect is small external R will also let (R||RI) become small, the cut-off frequency will be larger and degraded the bass-band performance. The other side effect is with extra power dissipation through the external resistor R to the ground. So using the external resistor R to flatting the variation of the cut-off frequency, the user must also consider the bass-band performance and the extra power dissipation to choose the accepted external resistor R value.
Power Supply Decoupling The G1427 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to make sure the output total harmonic distortion (THD) as low as possible. The optimum decoupling is using two capacitors with different types that target different types of noise on the power supply leads. For high frequency transients, spikes, a good low ESR ceramic capacitor works best, typically 0.1µF/1µF used and placed as close as possible to the G1427 VDD lead. A larger aluminum electrolytic capacitor of 10µF or greater placed near the device power is recommended for filtering low-frequency noise. Optimizing DEPOP Operation
C Input Input Signal IN R
Zi
Zf
Circuitry has been implemented in G1427 to minimize the amount of popping heard at power-up and when coming out of shutdown mode. Popping occurs whenever a voltage step is applied to the speaker and making the differential voltage generated at the two ends of the speaker. To avoid the popping heard, the bypass capacitor should be chosen promptly, 1/(CBx170kΩ) ≦ 1/(CI*(RI+RF)).
Figure 1
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Where 170kΩ is the output impedance of the mid-rail generator, CB is the mid-rail bypass capacitor, CI is the input coupling capacitor, RI is the input impedance, RF is the gain setting impedance which is on the feedback path. CB is the most important capacitor. Besides it is used to reduce the popping, CB can also determine the rate at which the amplifier starts up during startup or recovery from shutdown mode. De-popping circuitry of G1427 is shown as below Figure 2. The PNP transistor limits the voltage drop across the 120kΩ by slewing the internal node slowly when power is applied. At start-up, the voltage at BYPASS capacitor is 0. The PNP is ON to pull the mid-point of the bias circuit down. So the capacitor sees a lower effective voltage, and thus the charging is slower. This appears as a linear ramp (while the PNP transistor is conducting), followed by the expected exponential ramp of an R-C circuit. For better performance, CB is recommended to be at least 1.5 times of input coupling capacitor CI. For example, if using 1µF input coupling capacitor, 2.2µF ceramic or tantalum low-ESR capacitors are recommended to achieve the better THD performance.
G1427
Output coupling capacitor G1427 can drive clean, low distortion SE output power with gain –1V/V into headphone loads (generally 16Ω or 32Ω) as in Figure 3. Please refer to Electrical Characteristics to see the performances. A coupling capacitor is needed to block the dc-offset voltage, allowing pure ac signals into headphone loads. Choosing the coupling capacitor will also determine the -3dB point of the high-pass filter network, as Figure 4.
fC=1/(2πRLCC) For example, a 220µF capacitor with 32Ω headphone load would attenuate low frequency performance below 22.6Hz. So the coupling capacitor should be well chosen to achieve the excellent bass performance when in SE mode operation.
VDD VDD
Vo(PP)
CC RL Vo(PP)
Figure 3
VDD 100 kΩ 120 kΩ Bypass 100 kΩ
-3 dB
fc
Figure 2
Figure 4
Ver: 1.3 Sep 23, 2005
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Global Mixed-mode Technology Inc.
Bridged-Tied Load Mode Operation G1427 has two linear amplifiers to drive both ends of the speaker load in Bridged-Tied Load (BTL) mode operation. Figure 5 shows the BTL configuration. The differential driving to the speaker load means that when one side is slewing up, the other side is slewing down, and vice versa. This configuration in effect will double the voltage swing on the load as compared to a ground reference load. In BTL mode, the peak-to-peak voltage VO(PP) on the load will be two times than a ground reference configuration. The voltage on the load is doubled, this will also yield 4 times output power on the load at the same power supply rail and loading. Another benefit of using differential driving configuration is that BTL operation cancels the dc offsets, which eliminates the dc coupling capacitor that is needed to cancelled dc offsets in the ground reference configuration. Low-frequency performance is then limited only by the input network and speaker responses. Cost and PCB space can be minimized by eliminating the dc coupling capacitors.
G1427
Shutdown mode When the normal operation, the SHUTDOWN pin
should be held high. Pulling SHUTDOWN low will mute the outputs and deactivate almost circuits except PC-BEEP monitoring block. At this moment, the current of this device will be reduced to about 160µA to save the battery energy. The SHUTDOWN pin should never be left unconnected during the normal applications.
INPUT * HP/ LINE SE/ BTL SHUTDOWN
X Low Low High High X Low High Low High Low High High High High
AMPLIFIER STATE
INPUT OUTPUT
X Line Line headphone headphone Mute BTL SE BTL SE
* Inputs should never be left unconnected X= do not care
Input MUX And SE/ BTL Operation
VDD VDD
Vo(PP) RL 2xVo(PP) -Vo(PP)
VDD
PC-BEEP Operation The PC-BEEP input allows a system beep to be sent directly from a computer through the amplifier to the speakers with a few external components. It is activated automatically by detecting the PC-BEEP input. The preferred input signal is a square wave or pulse train with an amplitude of 1-VPP or greater. To be accurately detected, the signal must be with at least 1-VPP amplitude, 8 continuous rising edges, rise and fall times less than 0.1µs. When the signal is no longer detected, the amplifier will return its previous operating mode and volume setting. When the PC-BEEP mode is activated, both the LINEIN and HPIN are deselected and the outputs will be driven in BTL mode with the signal from PC-BEEP. The gain setting will be also fixed at 0.3V/V, independent of the volume setting. If the device is in the SHUTDOWN mode, activating PC-BEEP will take the device out of shutdown mode and output the PC-BEEP input signal until the PC-BEEP signal no longer detected. And then the device will return the shutdown mode when no PC-BEEP signal is detected. The PC-BEEP input can be dc-coupled to save the coupling capacitor. This pin is set at mid-rail normally when no signal is present. If AC-coupling is desired, the value of the coupling capacitor should be chosen to satisfy the equation: CPCB≧ 1/( 2πfPCB*150KΩ) CPCB is the PC-BEEP AC-coupling capacitor. fPCB is the frequency of applied PC-BEEP input signal.
Figure 5
The G1427 allows two different input sources applied to the audio amplifiers, which can be independent to the SE/ BTL setting. When HP/ LINE is held high, the headphone inputs are active. When the HP/ LINE is held low, the line inputs are selected. When SE/ BTL is held low, all four internal audio amplifiers are activated to drive the stereo speakers. When SE/ BTL is held high, two amplifiers are activated to drive the stereo headphones. The other two amplifiers are disable and keeping the outputs high impedance.
Ver: 1.3 Sep 23, 2005
TEL: 886-3-5788833 http://www.gmt.com.tw
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Global Mixed-mode Technology Inc.
Package Information
D 24
C
G1427
L
1.88
3.85
1.88
2.8
E1 E
0.71
1
Note 5
θ
A2 A1 e b
A
NOTE: 1. Package body sizes exclude mold flash protrusions or gate burrs 2. Tolerance ±0.1mm unless otherwise specified 3. Coplanarity : 0.1mm 4. Controlling dimension is millimeter. Converted inch dimensions are not necessarily exact. 5. Die pad exposure size is according to lead frame design. 6. Follow JEDEC MO-153
SYMBOL
A A1 A2 b C D E E1 e L y θ
MIN.
----0.00 0.80 0.19 0.09 7.70 6.20 4.30 ----0.45 ----0º
DIMENSION IN MM NOM.
--------1.00 --------7.80 6.40 4.40 0.65 0.60 ---------
MAX.
1.15 0.10 1.05 0.30 0.20 7.90 6.60 4.50 ----0.75 0.10 8º
MIN.
----0.000 0.031 0.007 0.004 0.303 0.244 0.169 ----0.018 ----0º
DIMENSION IN INCH NOM.
--------0.039 --------0.307 0.252 0.173 0.026 0.024 ---------
MAX.
0.045 0.004 0.041 0.012 0.008 0.311 2.260 0.177 ----0.030 0.004 8º
Taping Specification
PACKAGE
TSSOP-24 (FD)
Q’TY/REEL
2,500 ea
F e e d D ir e c tio n T y p ic a l T S S O P P a c k a g e O r ie n ta tio n
GMT Inc. does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and GMT Inc. reserves the right at any time without notice to change said circuitry and specifications.
Ver: 1.3 Sep 23, 2005
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